1. Field of the Invention
The present invention relates to a light-emitting device, for example, a field emission display.
2. Description of the Related Art
An example of field emission displays (FED) comprises a fluorescent screen panel 14 having red, green and blue fluorescent materials R, G and B which are arranged in stripes on a glass substrate 24, and a back panel 16, both of which are placed opposite to each other at a predetermined space therebetween, as shown in an exploded schematic perspective view of FIG. 33. The back panel 16 comprises cathode lines 17 having microchip cathodes 21 serving as field emission cathodes which are formed on a glass substrate 26, and gate electrode lines 19 provided at right angles to the cathode lines 17 through an insulating layer 18, as shown in an enlarged view of FIG. 34.
Both substrates 24 and 26 are placed opposite to each other at a predetermined space of several hundreds .mu.m, for example, 300 .mu.m, therebetween. The periphery of an image region is sealed by glass frit sealing so that the inside of the image region is maintained at ultra-high vacuum of 10.sup.-4 to 10.sup.-7 Pa.
In the field emission display having the above-described structure, generally, when a voltage is applied between cathode and gate electrodes to apply an electric field of 10.sup.8 to 10.sup.9 V/m to the cathode surface, electron beams are emitted from the tops of the microchip cathodes 21 by the tunnel effect through cathode holes. A potential is successively applied between the cathode and gate electrodes in a matrix structure in correspondence with the emission of the electron beams so that the emitted electron beams are applied to the selected fluorescent stripes R, G or B to make the stripes bright and display an image.
When the space between the cathode side substrate 26 and the fluorescent material side substrate 24 of the field emission display is in a high vacuum, as described above, a high pressure of 1 kg/cm.sup.2 is applied to the field emission display at atmospheric pressure. If a vacuum pressure resistance holding structure is not provided between the cathode side substrate 26 and the fluorescent material side substrate 24, the glass plate of each of both substrates 24 and 26 must have a thickness of several tens mm in order to make the field emission display resitant to this pressure.
In order to make the glass plate of each of both substrates 24 and 26 having a thickness of about 1 mm resistant to atmospheric pressure, it is thus necessary to provide a vacuum pressure resistance holding structure between both substrates 24 and 26, specifically, to arrange pillar- or block-formed vacuum pressure resistance holding spacers at intervals of several mm between both substrates 24 and 26.
Such spacers must have the properties that the spacers have high resistance to compressive stress and thus have resistance to atmospheric pressure of about 1 kg/cm.sup.2, that a uniform thickness can be maintained over the whole surface of the field emission display, that the spacers have no effect on the loci of electron beams emitted from cathodes, that the spacers less release gases and are stable in a vacuum, and that the spacers can resist to high-temperature treatment in frit sealing and baking.